1. Field of the Invention
The present invention relates to a technique for reproducing digital information, such as digital audio information, from a motion picture or movie film.
2. Description of the Prior Art
A movie film typically includes a plurality of graphic frames and an analog audio track. Analog audio information, which relates to a respective one or ones of the graphic frames, is recorded in the analog audio track. One example of a portion of such movie film is illustrated in FIG. 5.
The portion of a movie film 1 shown in FIG. 5 includes a graphic frame 2, a plurality of perforations 3 and an analog audio track 4. The plurality of perforations 3 are arranged with a substantially equal pitch in the vicinity of each of the righthand and lefthand sides of the movie film 1 and on opposite sides of the graphic frame 2. Such perforations 3 are utilized for transporting or taking up the movie film 1 in a predetermined direction by a transport mechanism (not shown). The analog audio track 4 is located in a portion of one side of the movie film 1, such as the portion between the graphic frame 2 and the righthand side perforations 3. Analog audio information is recorded in the analog audio track 4 in a longitudinal direction. Such analog audio information may be optically read out and converted into an audio signal.
Recently, to improve the sound quality of audio information reproduced from a movie film, a movie film has been developed in which analog audio information and digital audio information having the same content may be recorded thereon. One reason for the use of analog audio information in such movie film is to ensure compatibility with existing systems which may only be able to reproduce analog audio information and not digital audio information. One example of a portion of such movie film is illustrated in FIG. 6.
The portion of a movie film 100 shown in FIG. 6 includes a graphic frame 102, a plurality of perforations 103 and an analog audio track 104, which are substantially similar to those of FIG. 5. The movie film 100 further includes a first digital audio track 105 and/or a second digital audio track 106, which are located in a spare region or regions of the movie film. More specifically, the spare region for the first digital audio track 105 is a longitudinal spare region located between the lefthand perforations 103 and a lefthand film edge 100a and the spare region for the second digital audio track 106 is a longitudinal spare region located between the righthand perforations 103 and a righthand film edge 100b. Digital audio information may be recorded in either or both of the first and second digital audio tracks 105 and 106, respectively.
As is to be appreciated, the movie film 100 typically has a film running direction A, which is substantially perpendicular to a horizontal direction H.
Although FIG. 6 illustrates both the first and second digital audio tracks 105 and 106, respectively, the movie film 100 may have only one of such digital audio tracks, as previously described. Alternatively, only one of these digital audio tracks may be utilized to record digital audio information therein.
Each of the first and second digital audio tracks 105 and 106, respectively, may be utilized to record four channels of right and left digital audio signals therein. Accordingly, by utilizing both the first and second digital audio tracks 105 and 106, respectively, four channels of right and left digital audio signals, for a total of eight channels, may be recorded therein.
An example of the audio signals recorded as digital information is shown in FIG. 7A. As shown therein, such recorded digital information is formed as a plurality of data cells or so-called pits 7 having a predetermined shape, such as the square shape shown in FIG. 7A. Each such pit 7 corresponds to one bit of digital information. The pits 7 are typically arranged in a plurality of rows in which each of the rows is horizontally arranged such as in the horizontal direction H in the digital audio track which is substantially perpendicular to the film running direction A.
Since the recorded digital information is normally optically read out as hereinafter more fully described, the pits 7 may have dichroic (or density) information recorded therein so as to affect the transmissivity of light through the respective digital audio track of the movie film 100. As a result, relatively low "0" and relatively high "1" digital bits may be readily distinguished. An example of such situation is illustrated in FIG. 7A, wherein the hatched pits correspond to the digital 0 bit whereas the blank pits correspond to the digital 1 bit.
The audio information recorded in the analog audio track 104 and the first and/or second digital audio tracks 105 and 106, respectively, of the movie film 100 may be read out or reproduced therefrom. FIG. 8 illustrates an apparatus 10 for reproducing digital audio information, such as that recorded in the first and second digital audio tracks 105 and 106. An apparatus for reproducing the analog audio signals, such as those recorded in the analog audio track 104, is well known and, thus, will not be described herein.
As shown in FIG. 8, the reproducing apparatus 10 includes a light source or a halogen lamp 11, a lens 12, a linear light receiving element or line sensor 13 of a charge coupled device (CCD), a filter 14, an equalizer 15, a comparator 16, a clock extractor 17, a data extractor 18, and a driver 20. Such apparatus 10 will be described below.
An optical beam from the halogen lamp 11 is guided through the lens 12 so as to irradiate the first digital audio track 105 (or second digital audio track 106) of the movie film 100. As a result, the beam is modulated by the pit information recorded in the digital audio track 105. The modulated beam is focused on the linear light receiving element or line sensor 13 of the CCD, or similar such device, so that the digital information (or pit column information) may be read out and converted into corresponding electrical signals. Since the movie film 100 is advanced or taken up in a direction A indicated in FIG. 6, which is normal to the drawing surface, the light receiving element 13 reads out digital audio information in line units.
The signals from the light receiving element 13 are supplied through the filter 14 so as to restrict the working frequency band thereof (such filter may be a low pass filter) and the equalizer 15 so as to equalize the received signals. After which, the "1" and "0" signals, corresponding to the read pits 7, from the equalizer 15 are supplied to the comparator 16 so as to be compared with a reference level. Pit column signals from the comparator 16 are supplied to the clock extractor 17 to extract or reproduce clock signals therefrom. The signals from the comparator 16 are further supplied to the data extractor 18 to extract or reproduce audio signals therefrom.
The driver 20 for the light source 11 includes a power source 21, a regulator 22 and a fan 23. As shown in FIG. 8, an AC power signal is supplied to the power source 21 and transformed thereat into a predetermined AC voltage. The AC voltage from the power source 21 is stabilized by the regulator 22, and a stabilized AC voltage therefrom is supplied to the halogen lamp 11 so as to cause the halogen light to be lit. By stabilizing the AC voltage, the optical intensity of the halogen light 11 is stabilized. Since the halogen lamp 11 generates a relatively large amount of heat while in a running mode, the cooling fan 23 is provided so as to remove some of this heat.
As previously described, the reproducing apparatus 10 typically utilizes a halogen lamp, or similar such device, for the light source 11. Such halogen lamp has a relatively short operating life, that is, approximately 50 hours. Additionally, such halogen lamp is relatively expensive.
Further, to drive the halogen lamp 11, the driver 20 includes not only the power source circuit 21 but also the regulator 22 and the fan 23, as previously described. As is to be appreciated, the peripheral circuits associated therewith are relatively complicated. As a result, the driver 20 is relatively expensive and has a relatively large-size, thereby causing the apparatus 10 to be relatively expensive and to have a relatively large size.
Furthermore, the CCD, of the linear light receiving element 13, has to be exemplified by a one-dimensional sensor. Accordingly, the cost of such linear light receiving element is relatively high.
Thus, the prior art has failed to provide an apparatus for reproducing digital information from a movie film having a light source with a relatively long life, a relatively simple peripheral circuit(s) associated with the light source, and which has a relatively low cost.